ABSTRACT Hypoxia-ischemia (HI) is the one of leading causes of neurodevelopmental morbidities in preterm and full term infants. The only therapeutic strategy to treat HI encephalopathy (HIE) is hypothermia in full term infants, which is only partially protective, and treatment does not exist for HI exposed preterm infants except for supportive care. Based upon the Stroke Therapy Academic Industry Roundtable (STAIR) criteria, sufficient dose-response and therapeutic time windows, adequate histological and behavioral outcomes, and understanding mechanism(s) of action for neuroprotectants are necessary for preclinical drug development to facilitate translation of neuroprotective strategies from animals to humans. The basis of this proposal is the identification of novel immunomodulatory proteins, Inter-alpha Inhibitor Proteins (IAIPs) that are currently in development as effective therapeutic agents in systemic inflammation/shock syndromes. IAIPs are novel anti- inflammatory molecules that broadly inhibit destructive serine proteases, robustly block pro-inflammatory cytokines, augment anti-inflammatory cytokine production, and block complement activation during systemic inflammation. Our exciting preliminary studies using blood derived IAIPs suggest IAIPs have remarkable neuroprotective properties in HI-neonatal rats. However, information regarding mechanism(s) for the neuroprotective efficacy of IAIPs and their brain penetration in HI-brain injury in neonates has not been previously elucidated. The purpose of this proposal is to fill these gaps of knowledge: (1) To determine the optimal dose-response and therapeutic time windows for IAIPs in neonatal rats; (2) To assess short/long term neurobehavioral outcomes, and establish the optimal neuroprotective efficacies for IAIPs administration in neonates; (3) To examine operative and molecular mechanism(s) of IAIPs as related to inflammation, cell death, blood-brain barrier (BBB) permeability, glial cellular responses, and penetration IAIPs into brain after HI brain injury. The well-characterized Rice-Vannucci neonatal HI model will be used. The neuroprotective efficacy with various doses and time windows of IAIPs treatment will be determined by comparing brain injury/neuronal death (Luxol fast blue/H&E and DNA fragmentation). Mechanism(s) of action will be examined by determining inflammation (pro-inflammatory cytokine production/neutrophil brain infiltration), apoptosis, BBB permeability, IAIP brain penetration (125I-labeled IAIPs), glial cell responses (astrogliosis, microglia activation, and oligodendrocyte injury), and possible side effects on clotting/fibrinolysis cascades. Short/long-term behavioral outcomes will be determined at different stages of brain development. The current proposal will establish drug efficacy, optimal dose-responses and time windows, during which IAIPs attenuate HI brain injury with reduced neuroinflammation, neuronal/glial cell death, and BBB damage, and improve short/long term behavioral performance in neonatal HI rats. Results should yield novel preclinical information to accelerate IAIPs use as neuroprotective agents to treat HI-related brain injury in human premature and full term infants.